How to Test look and feel ?

Is a tool actually entirely necessary? All you actually need is to decide which platform is your baseline and then open the site using each of the browsers for comparison.
There are many ways in which you can do this, if you really have to do it. From your description, I am assuming that from look and feel you mean to say your web application is working properly on different browsers or not. Now if you want to make sure that all the objects/page-elements are available on the different browsers you can use tools like Selenium Remote Control ( Brief overview at testinggeek.com/seleniumrc.asp) but if you also want to find out that rendering is proper you need to find tools which support image comparison. But as Martin has suggested, do not do it if you do not do it. Hope it helps.

Well fisrt of all, you may want to consider some sort of virtualization (like using VMWare) so that you can set up for different screen resolutions and browser versions. Remember that while we are at IE7, IE6 is still very common and will probably still be in the majority, so this is another requirement.

I am actually using TestComplete right now myself and it allows you to take a snapshot of certain areas of the screen. It also allows you to do pixel comparisons, so you can confirm whether colors defined in your stylesheets, etc., are appearing the same across all browsers.

If you're looking for something to automate the confirmation of the layout design then this would be a good choice, and it's also cheap. They have like a 30-day trial too, so you can check and make sure it'll work for your application.